Deuterated diborane (B2DxH6-x), where x is 2 to 6, is a versatile reagent with broad applications in organic and inorganic syntheses. Because deuterated diborane is a pyrophoric gas having a flash point of about −90° C. and an autoignition temperature of about 38° C. to 51° C., borane complexes with Lewis bases are typically used instead, as they are more convenient to handle. Numerous examples of these borane complexes for use in the synthesis of pharmaceuticals and other industrial applications are well known in the art. Deuteroborane-tetrahydrofuran complex (referred to as “BD-THF” or “BD-THF complex”) is especially suitable for use as borane-Lewis base complexes for synthetic applications, such as hydroboration of carbon-carbon double and triple bonds, and reduction of various functional groups used in the preparation of tracer compounds and compounds having improved functionality.
Problematically, BD-THF solutions having a concentration in excess of about 2.0 moles per liter (“M”) readily release diborane (where diborane includes the deuterated and partially deuterated forms). Under the United States Department of Transportation (“DOT”) regulations, transportation of a package containing a material which is likely to decompose with a self-accelerated decomposition temperature (SADT) of 50° C. or less with an evolution of a dangerous quantity of heat or gas when decomposing is prohibited unless the material is stabilized or inhibited in a manner to preclude such evolution. Because of the intrinsic instability and low autoignition temperature, BD-THF solutions having a concentration in excess of about 1M generally cannot meet the SADT mandated by the DOT. Aside from resulting in unacceptable SADT temperatures, diborane exhibits high vapor pressure at room temperature resulting in overpressurization of storage containers. Moreover, diborane can attack the tetrahydrofuran (“THF”) cyclic ether linkage causing ring opening thereby resulting in less pure BD-THF and concomitant heat generation and container pressurization.
Another problem associated with BD-THF complexes is short shelf life, especially at temperatures at or above normal room temperature of about 25° C. BD-THF complexes can decompose during shipping or in storage if they are not stabilized properly, or are shipped at elevated temperature.
In the interest of conservation of resources and efficient use of reactor vessels, one would like to conduct reactions at the highest concentration possible for a particular reaction. In that regard, low BD-THF concentration leads to low reactor loading and inefficient use of equipment.
A need exists for concentrated stabilized BD-THF solutions suitable for the use in the preparation of deuterated organic and inorganic compounds.